Indomethacin-containing external preparations have conventionally been commercialized in various forms, including gels, creams, and liquids. These product forms have their own characteristics. For example, gels and liquids dissolve indomethacin therein quite well because they contain large amounts of alcohol. Also, gels and liquids exhibit good percutaneous absorption property. However, when gels are applied to the skin, due to their inherent structure, gels tend to remain on the skin unevenly, resulting in unfavorable sensation and poor feeling of use. In contrast, creams contain large amounts of oily ingredients, which do not leave stickiness after use. Therefore, creams ensure good feeling of use. However, since creams can dissolve only insufficient amounts of indomethacin therein, they exhibit poor percutaneous absorption as compared with gels. Liquids have been widely employed because they provide excellent percutaneous absorption. However, they have disadvantages, including slow drying after application, causing running of the liquid preparation.
According to known typical practice, sulfites such as sodium bisulfite or similar additives are added to indomethacin-containing liquid preparations in order to prevent color change of the preparations or to decrease reduction in indomethacin content (Patent Document 1). However, when liquid preparations containing both indomethacin and a sulfite are stored at a low temperature, crystals are precipitated with time. To prevent this phenomenon, a variety of precipitation preventive measures have been employed.
In order to prevent crystal precipitation of indomethacin-containing external liquid preparations, several approaches have heretofore been proposed. Examples of products which are produced through such known techniques include an indomethacin-containing external liquid preparation in which a lower alcohol-water vehicle formed of indomethacin, a vitamin E compound, and a middle-chain fatty acid ester (which serves as a percutaneous absorption enhancer) is employed as a base composition of the preparation, and a surfactant such as polyoxyethylene hydrogenated castor oil is incorporated thereto (Patent Document 2); and an external liquid preparation in which indomethacin is combined with additives such as a lower alcohol (or acetone), crotamiton, and glycols (Patent Document 3). However, use of surfactants such as polyoxyethylene hydrogenated castor oil, or crotamiton is desirably avoided, because they might irritate the skin.
As mentioned above, there have not yet been provided satisfactory indomethacin-containing external liquid preparations which provide good feeling of use, which exhibit high percutaneous absorption of the active ingredient, and which under any conditions do not cause precipitation of crystals with time.    [Patent Document 1] JP-A-SHO59-88419    [Patent Document 2] JP-A-HEI6-9394    [Patent Document 3] JP-A-SHO58-124716